Various types of network connection interfaces have been developed. For example, when a printer and a network are connected, a parallel interface can be used for directly connecting the printer and a personal computer. Further, a wireless LAN can perform a printing operation by connecting a wireless LAN printer server to a personal computer.
In JP-A-2004-62245, a wireless LAN printer server, which includes a LAN port and a parallel port or serial port, is connected to the printer. Data is transmitted or received via an Ethernet (R) port functioning as a signal line. Power is supplied from a connection apparatus to an accessory via the parallel port or serial port functioning as a power line.
However, since a wireless LAN printer server is developed after development of a printer, it is necessary to connect the wireless LAN printer server to the conventional printer. Therefore, in many cases, a wireless LAN printer server becomes a separate option attached to an outside of a printer. In the wireless LAN printer server, power is supplied from a designated adaptor, and printing data is transmitted or received via a parallel interface (a parallel port).